It is known to equip a vehicle such as a passenger car with an air bag for protecting a vehicle occupant. In case of deploying the air bag with a predetermined operation force in order to protect the vehicle occupant, an appropriate effect may not be obtained due to a seat status such as a seat position (i.e. occupant position in the vehicle). Thus, it has been proposed to switch the operation force of the air bag in response to the seat status when the air bag is deployed. A vehicle seat equipped with a seat status detecting device for detecting the seat status is also known.
Such seat status detecting device is disclosed in U.S. Pat. No. 6,053,529. The disclosed seat status detecting device includes a magnetic sensor mounted to a stationary rail of a seat slide portion via a support member, and a detected plate (flange) mounted to a movable rail of the seat slide portion. The magnetic sensor is operative to sense the seat position with respect to two zones. The magnetic sensor generates a signal as a seat position detection signal in response to the position of the detected plate with respect to two zones. Then, the seat status detecting device detects the seat position based on the seat position detection signal generated by the magnetic sensor.
According to the above-mentioned seat status detecting device, the support member and the detected plate are employed for mounting the magnetic sensor to the stationary rail. In addition, a space formed along the stationary rail and the movable rail by the magnetic sensor and the detected plate is a dead space, thereby deteriorating the mounting performance of the magnetic sensor.
In order to prevent an increase of number of parts and improve the mounting performance of the magnetic sensor, a known seat status detecting device is disclosed in Japanese Patent Laid-Open Publication No. 2002-200933. According to the disclosed seat status detecting device, a magnetic sensor is mounted to an upper rail (movable rail) for detecting a lower rail (stationary rail) so as to detect the seat position.
Both seat status detecting devices mentioned above detect the seat position by a magnetic member (detected plate or stationary rail) such as a steel plate approaching the magnetic sensor. Therefore, if a foreign object of magnetic member such as an iron piece and magnet that the occupant has brought into the vehicle attaches to the magnetic sensor, the detection performance thereof may deteriorate.
Thus, a need exists for a seat status detecting device that can prevent the detection performance of a magnetic sensor from deteriorating caused by a foreign object of magnetic member attaching to the magnetic sensor.